Electronic thermometers for measuring a patient's body temperature via a slim temperature probe have been in use for quite some time and have proven their worth in health care facilities as well as in the hands of patients themselves. Typically this type of thermometer includes a portable base housing having a processor for processing data provided by sensing elements generally located at the tip end of a rather small diameter probe. The patient temperature is determined from the data and displayed visually upon a viewing screen such as an LCD. Electronic thermometers of this type are disclosed in detail in U.S. Pat. Nos. 5,632,555; 6,000,846; 6,036,361; 6,827,488 and 6,971,790, the disclosures of which are incorporated herein by reference and are commercially available through Welch Allyn, Inc. which is the common assignee of these patents.
As noted in the above mentioned prior art patents, the tip end of the sensing probe is generally equipped with a heater for bringing the tip up to a desired threshold temperature and a temperature sensor for providing accurate information concerning the actual tip temperature. The response time of the tip is typically four seconds or more. Because of the limited space available inside the probe tip, mounting the heater and the heat sensing element within the tip has proven to be difficult. Epoxy bonds are used to secure the heater and the heat sensor to the interior surface of the tip. Some epoxies degrade with use, and the heater elements tend to overheat causing both epoxy and solder bonds to fail. In addition some epoxies are not good thermal conductors and thus can disrupt the heat flow through the tip producing erroneous temperature readings. A thermistor is generally provided in the heater circuitry to insure that the heater does not overheat, however, the use of the thermistor increases the overall cost of the system.